This invention relates to electroslag welding machines and more particularly to an improvement in nozzle structures of the electroslag welding machines for use in welding large sized planks having heavier thicknesses.
Recently, with the increase of large sized machines such as steam boilers, heavy mechanical presses and rolling mills, large sized components are needed for the fabrication of the machines.
It has been known that an electroslag welding method can be used in making large sized components having as large as 150 to 300 mm thickness by joining two planks with the electroslag welding method, which is described in Japanese Laid Open Print of Patent Application No. 48-47467 (Application Ser. No. 46-83591). In this prior method, a plurality of consumable nozzle plates are vertically placed within a weld gap formed by faces of planks to be welded. However, these nozzle plates are consumed as welding progresses and it is needed to hang a plurality of long nozzle plates within the weld gap while welding.
Another method usually used in welding planks is an electroslag welding method (not consumable nozzle type) in which a nozzle or a plurality of nozzles are inserted within a weld gap formed by faces of planks to be welded from one side of the weld gap, and wires are continuously fed to the weld gap through the nozzles keeping pace with welding progress. The nozzles move upward within the weld gap while oscillating along the weld. An example of the prior method is described in "Electroslag Welding", by Paton page 191 to 212. However, in the conventional electroslag welding machine, each nozzle is separated and dependently supported to the welding machine. The stiffness of the nozzle depends on the length of the nozzle pipe projecting out from the welding machine into the weld gap. Therefore, when a conventional nozzle is elongated for use in welding large planks having heavier thickness, the stiffness of the nozzle decreases and a short circuit may appear between the nozzle and the planks to be welded by the sag or the rocking motion of the nozzle structure.